This invention relates to a composite of two or more biocompatible polymers, at least one of which is polytetrafluoroethylene (PTFE) and the other component being a bioabsorbable polymer. The nonabsorbable PTFE is used in the composite as a reinforcing binder. The reinforcing binder is a network of unsintered, interconnected microfibers. The microfibers can be formed, for example, by blending with a thermoplastic polymer vehicle, such as polymethylmethacrylate. The bioabsorbable polymer component can be present in the form of a particulate filler contained within the PTFE microfibrillar structure. The bioabsorbable particulate component can be micropulverized and could be, for example, polyglycolic acid (PGA), polylactic acid (PLA), a homo- or copolymer of trimethylene carbonate (TMC), and blends of the same or similar polymers. The polymethylmethacrylate is subsequently extracted with a suitable solvent. The resulting microporous structure has a tortuous porosity.
Alternatively, the bioabsorbable polymer can serve as the thermoplastic vehicle during the PTFE fibrillation process thus resulting in a nonporous reinforced composite structure. The bioabsorbable polymer vehicle component could be a copolymer of polyglycolic acid and trimethylene carbonate (GLY/TMC) or other bioabsorbable thermoplastic.
The composite described in this application may be useful in many biomedical applications, such as a tissue, hernia, or ligament repair device, a burn or wound dressing, a pledget, a drug delivery system and a tubular article, for example a vascular graft. The bioabsorbable component enhances tissue ingrowth within the fibrillar PTFE matrix. The nonabsorbable microfibrillar PTFE matrix provides additional support, direction and strength to the natural tissue formation.
The composite polymer structure described in this invention is useful in biomedical applications, such as in tissue repair, hernia repair, ligament repair, burn and wound dressing, pledgets, drug delivery systems, vascular grafts, etc. The bioabsorbable component enhances tissue ingrowth within the fibrillar PTFE matrix, which provides additional support, direction and strength to the natural tissue formation.
An advantage of this invention is that since a thermoplastic vehicle is used to form the fibrillar PTFE matrix, it therefore can be extruded into many different shapes such as a rod, tube, tape, film, or other intricate forms before extracting the thermoplastic.
Another advantage is that the PTFE is unsintered. Thus, the break down temperature of known bioabsorbable polymers (e.g., less than about 250.degree. C.) is avoided in the processing of the composite of this invention.
The completely fibrillated, unsintered polytetrofluoroethylene (PTFE) reinforcing binder of this invention has advantages over a prior art porous, sintered PTFE product. For a disclosure of a sintered PTFE product, see, e.g., "Fluorocarbons Available in New Fibrous, Porous Configurations" published in Materials In Design Engineering, pages 5-7, May, 1965, which is incorporated herewith by reference.
Some of the advantages of this invention, in summary form, are as follows. A filler can be added directly to the PTFE polymer without subjecting it to the detrimental effects of the sintering temperature (approximately 325.degree. F.) of PTFE. Also, a level as high as 97% filler content in the unsintered PTFE polymer can be achieved.
The prior art describes methods of preparation and nonbiological uses of fibrillar PTFE. The nonbiological uses include electrochemical applications. See, e.g., U.S. Pat. Nos. 3,527,616; 3,407,249; and 3,407,096 which are incorporated herein by reference.
A composite material for use with mammalian tissue has been invented. The composite material comprises:
a) an unsintered, microfibrillar, nonabsorbable biocompatible component prepared from polytetrafluoroethylene, and
b) a bioabsorbable component manufactured from a polymer prepared from one or more monomers selected from the group consisting of lactides, carbonates, oxalates and lactones, and optionally
c) a nonabsorbable, biocompatible thermoplastic component manufactured from a polymer which is liquid at a temperature from about 150.degree. to 200.degree. C. and solid at ambient temperature, and which provides additional integrity to the unsintered component. In one embodiment, the bioabsorbable component is selected from the group consisting of lactides, carbonates and lactones. In a specific embodiment, the lactides are selected from the group consisting of glycolide and 3,6-dimethyl-1,4-dioxane-2,5-dione; the carbonate is 1,3-dioxan-2-one; and the lactones are selected from the group consisting of .epsilon.-caprolactone and 1,4-dioxan-2-one. In another embodiment, the bioabsorbable component is manufactured from glycolide.
In combination with any of the above embodiments, other embodiments are the bioabsorbable component enmeshed in the pores of the unsintered component; the composite material in the form of a sheet or a hollow tube; and the nonabsorbable, thermoplastic component being poly(ethylenevinylacetate).
Still another embodiment is wherein the nonabsorbbable, thermoplastic component is enmeshed in the pores of the unsintered component. In a specific embodiment, the nonabsorbable, thermoplastic component is poly(ethylenevinyl acetate).
An alternative composite material for use with mammalian tissue has also been invented. The alternative composite material comprises:
a) an unsintered, microfibrillar, non-absorbable biocompatible component prepared from polytetrafluoroethylene, and
b) a particulate bioabsorbable component manufactured from a polymer prepared from one or more monomers selected from the group consisting of lactides, carbonates, oxalates and lactones, and optionally
c) a non-absorbable, biocompatible thermoplastic component manufactured from a polymer which is liquid at a temperature from about 150.degree. to 200.degree. C. and solid at ambient temperature, and which provides additional integrity to the unsintered component. In one embodiment, the particulate bioabsorbable component is selected from the group consisting of lactides, carbonates and lactones. In a specific embodiment, the lactides are selected from the group of glycolide and 3,6-dimethyl-1,4-dioxan-2,5-dione; the carbonate is 1,3-dioxan-2-one: and the lactones are selected from the group consisting of .epsilon.-caprolactone and 1,4-dioxan-2-one. In another embodiment, the bioabsorbable component is manufactured from glycolide.
In combination with any of the above embodiments, other embodiments are the particulate bioabsorbable component being micropulverized; the composite material in the form of a sheet or a hollow tube; and the nonabsorbable, thermoplastic component being poly(ethylene-vinyl acetate).
Another alternative composite material for use with mammalian tissue has also been invented. The other alternative composite material comprises a first part consisting of the two component and optional three component composite material described above; and a second part affixed to at least one side of the first part. The second part comprises a bioabsorbable textile reinforcement component. The bioabsorbable reinforcement component is woven or knitted, and is manufactured from the same or a different polymer than the bioabsorbable component of the first part. In one embodiment, the bioabsorbable textile reinforcement component is selected from the group consisting of lactides, carbonates and lactones. In a specific embodiment, the lactides are selected from the group consisting of glycolide and 3,6-dimethyl-1,4-dioxan-2,5-dione; the carbonate is 1,3-dioxan-2-one; and the lactones are selected from the group consisting of .epsilon.-caprolactone and 1,4-dioxan-2-one. In another embodiment, the textile reinforcement material is affixed to both sides of the first part. In a specific embodiment, the reinforcement material is laminated to the first part.
A drawing which describes the shape and/or geometrical configuration of the composite material is not necessary for an understanding of this invention. That is, any person skilled in the composite art will know how to manufacture and how to use the invention by reading this specification generally, and the examples specifically.